Although it may be applied to any micromechanical components and structures, in particular to sensors and actuators, the present invention and the underlying problem are elucidated with reference to a micromechanical yaw rate sensor or acceleration sensor having a trenched micromechanical function layer that is manufacturable using silicon surface micromachining technology.
Both surface and volume micromechanical process steps are performed with such micromechanical components. Volume micromechanical processes are used in processing the back of components. To do so, the wafer with its front side already structured is rotated and placed with this side on handler systems or instrument mounts.
There may be contamination of the front side, i.e., particles may be deposited on the structured surface. In subsequent front side etching processes, these particles can be transferred to the underlying layers. The subsequent process steps may result in freely mobile particles which impair the functioning of the respective micromechanical component.
A method has been proposed for using a temporary protective layer made of aluminum to protect the front side while processing the back. After processing the back, this protective layer is removed by a wet chemical process during which particles on the surface are underetched and lifted. However, this process is complicated and expensive, because additional process steps and mask levels are required.